Preliminary results from the longitudinal dispersion compensation system for the CHARA array

David H. Berger; Theo Armand ten Brummelaar; William G. Bagnuolo Jr.; Harold A. McAlister

doi:10.1117/12.457161

21 February 2003 Preliminary results from the longitudinal dispersion compensation system for the CHARA array

David H. Berger, Theo Armand ten Brummelaar, William G. Bagnuolo Jr., Harold A. McAlister

Proceedings Volume 4838, Interferometry for Optical Astronomy II; (2003) https://doi.org/10.1117/12.457161
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

Abstract

The Center for High Angular Resolution Astronomy (CHARA) has constructed an array of six alt-az telescopes at Mount Wilson Observatory in southern California. Together with the central beam combining facility, the telescopes operate as an optical/near-infrared interferometer with a maximum baseline of 330 meters. Due to practicality and cost constraints, some of the long path delay required for path length compensation occurs out of vacuum. A consequence is a spectrally dispersed beam along the optical axis which decreases fringe contrast. To combat this visibility loss, wedges of glass are placed in the beam to chromatically equalize path lengths. Each set of glass wedges is called a Longitudinal Dispersion Compensator (LDC). The design and fabrication phases for the LDC systems are described. Beginning with the material selection process, a glass with similar dispersive qualities to air within the observing bandwidths was selected. Next was the optomechanical design which included custom engineered optical mounts for the glass wedges, high precision translation stages for automated thickness variation and calibration adjustments. Following this, the hardware driver, software controls, and the user interface were written. Finally, the LDC components were assembled, integrated into the Beam Synthesis Facility, and tested. The quantified results are presented and demonstrate an improvement to the interferometric measurements.

Citation Download Citation

David H. Berger, Theo Armand ten Brummelaar, William G. Bagnuolo Jr., and Harold A. McAlister "Preliminary results from the longitudinal dispersion compensation system for the CHARA array", Proc. SPIE 4838, Interferometry for Optical Astronomy II, (21 February 2003); https://doi.org/10.1117/12.457161

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